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Search Results: 1 - 10 of 410 matches for " Valder;Palomino "
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Probabilistic Neural Network and Fuzzy Cluster Analysis Methods Applied to Impedance-Based SHM for Damage Classification
Lizeth Vargas Palomino,Valder Steffen Jr.,Roberto Mendes Finzi Neto
Shock and Vibration , 2014, DOI: 10.1155/2014/401942
Abstract: Impedance-based structural health monitoring technique is performed by measuring the variation of the electromechanical impedance of the structure caused by the presence of damage. The impedance signals are collected from patches of piezoelectric material bonded on the surface of the structure (or embedded). Through these piezoceramic sensor-actuators, the electromechanical impedance, which is directly related to the mechanical impedance of the structure, is obtained. Based on the variation of the impedance signals, the presence of damage can be detected. A particular damage metric is used to quantify the damage. Distinguishing damage groups from a universe containing different types of damage is a major challenge in structural health monitoring. There are several types of failures that can occur in a given structure, such as cracks, fissures, loss of mechanical components (e.g., rivets), corrosion, and wear. It is important to characterize each type of damage from the impedance signals considered. In the present paper, probabilistic neural network and fuzzy cluster analysis methods are used for identification, localization, and classification of two types of damage, namely, cracks and rivet losses. The results show that probabilistic neural network and fuzzy cluster analysis methods are useful for identification, localization, and classification of these types of damage. 1. Introduction Failures occurring in industrial equipment and structures in general are associated with friction, fatigue, impact, and crack growth or with other reasons. For an appropriate functioning of the system, the failure should be located and repaired timely. In general terms, the problem of damage monitoring consists in locating and measuring the fault and estimating the remaining life of the system (damage prognosis). One of the most important ambitions of modern engineering is to perform structural health monitoring in real time in structural components of high cost and considerable responsibility. Thus, the creation or improvement of techniques that enhance the accuracy and reliability of the tracking process is highly desirable and is the subject of several studies both in industry and academic environments [1]. There are several techniques for monitoring the occurrence and propagation of structural damage. One of these techniques is the so-called impedance-based structural health monitoring [2]. The basic idea behind this technique is monitoring the changes in the mechanical impedance of the structure as caused by the presence of damage. As the direct measurement of the
Architecture of a remote impedance-based structural health monitoring system for aircraft applications
Martins, Luiz G. A.;Finzi Neto, Roberto M.;Steffen Jr., Valder;Palomino, Lizeth V.;Rade, Domingos A.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2012, DOI: 10.1590/S1678-58782012000500008
Abstract: the essence of structural health monitoring (shm) is to develop systems based on nondestructive inspection (ndi) technologies for continuous monitoring, inspection and detection of structural damages. a new architecture of a remote shm system based on electromechanical impedance (emi) measures is described in the present contribution. the proposed environment is employed to automatically monitor the structural integrity of aircrafts and is composed by sensor networks, a signal conditioning system, a data acquisition hardware and a data processing system. the obtained results allow the accomplishment of structural condition-based maintenance strategies, in opposite to those based only on the usage time of the equipment. this approach increases the operational capacity of the structure without compromising the security of the flights. as the environment continually checks for the first signs of damage, possibly reducing or eliminating scheduled aircraft inspections, it could significantly decrease maintenance and repair expenses. furthermore, the usage of this system allows the creation of a historical database of the aircrafts structural integrity, making possible the incremental development of a damage prognosis system (dps). this work presents the proposed architecture and a set of experiments that were conducted in a representative aircraft structure (aircraft window) to demonstrate the effectiveness of the proposed system.
Biossimilares necessitam de dados clínicos comparativos cientificamente confiáveis Biosimilars require scientifically reliable comparative clinical data
Valderílio Feijó Azevedo
Revista Brasileira de Reumatologia , 2013,
Abstract:
Genome analysis of Mexican flora
Palomino Guadalupe
Genetics and Molecular Biology , 2000,
Abstract:
Tango, samba and love Tango, samba y amor
Pablo Palomino
Apuntes de Investigación del CECYP , 2008,
Abstract: This article proposes an explanation of the centrality of love in the poetic structure of tango and samba based on the modernization of the cities of Buenos Aires and Rio de Janeiro in the 1920’s. Through the analysis of lyrics from both genres, and a survey of Argentine and Brazilian historiographies of popular music, this article lays out a transnational perspective about the making of urban popular cultures of the early Twentieth Century, and also provides a reflection on music as an historiographic object. Este artículo plantea la centralidad de la temática amorosa en el tango y el samba de entreguerras como consecuencia de las características de la modernización de Buenos Aires y Rio de Janeiro alrededor de los a os 20. A través del análisis de algunas letras de ambos géneros, y de un recorrido por ciertos textos clave de la historiografía argentina y brasile a dedicada a la historia de la música popular, se proponen las bases para una mirada transnacional sobre la construcción de las culturas populares urbanas del siglo veinte, así como una reflexión acerca de la música como objeto historiográfico.
Sobre creatividad e historia cultural en la historiografía musical latinoamericana reciente
Pablo Palomino
Apuntes de Investigación del CECYP , 2009,
Abstract:
A comparison between two logical formalisms for rewriting
Miguel Palomino
Computer Science , 2006,
Abstract: Meseguer's rewriting logic and the rewriting logic CRWL are two well-known approaches to rewriting as logical deduction that, despite some clear similarities, were designed with different objectives. Here we study the relationships between them, both at a syntactic and at a semantic level. Even though it is not possible to establish an entailment system map between them, both can be naturally simulated in each other. Semantically, there is no embedding between the corresponding institutions. Along the way, the notions of entailment and satisfaction in Meseguer's rewriting logic are generalized. We also use the syntactic results to prove reflective properties of CRWL.
Optimal Task Placement of a Serial Robot Manipulator for Manipulability and Mechanical Power Optimization  [PDF]
Rogério Rodrigues dos Santos, Valder Steffen, Sezimária de Fátima Pereira Saramago
Intelligent Information Management (IIM) , 2010, DOI: 10.4236/iim.2010.29061
Abstract: Power consumption and accuracy are main aspects to be taken into account in the movement executed by high performance robots. The first aspect is important from the economical point of view, while the second is requested to satisfy technical specifications. Aiming at increasing the robot performance, a strategy that maximizes the manipulator accuracy and minimizes the mechanical power consumption is considered in this work. The end-effector is constrained to follow a predefined path during the optimal task positioning. The proposed strategy defines a relation between mechanical power and manipulability as a key element of the manipulator analysis, establishing a performance index for a rigid body transformation. This transformation is used to compute the optimal task positioning through the optimization of a multicriteria objective function. Numerical simulations regarding a serial robot manipulator demonstrate the viability of the proposed methodology.
Multimodal vibration damping through piezoelectric patches and optimal resonant shunt circuits
Viana, Felipe Antonio C.;Steffen, Jr, Valder;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2006, DOI: 10.1590/S1678-58782006000300007
Abstract: piezoelectric elements connected to shunt circuits and bonded to a mechanical structure form a dissipation device that can be designed to add damping to the mechanical system. due to the piezoelectric effect, part of the vibration energy is transformed into electrical energy that can be conveniently dissipated. therefore, by using appropriate electrical circuits, it is possible to dissipate strain energy and, as a consequence, vibration is suppressed through the added passive damping. from the electrical point of view, the piezoelectric element behaves like a capacitor in series with a controlled voltage source and the shunt circuit, commonly formed by an rl network, is tuned to dissipate the electrical energy, more efficiently in a given frequency band. it is important to know that large inductances are frequently required, leading to the necessity of using synthetic inductors (obtained from operational amplifiers). from the mechanical point of view, the vibration energy can be attenuated in a single mode, or in multiple modes, according to the design of the damping device and the frequency band of interest. this work is devoted to the study of passive damping systems for single modes or multiple modes, based on piezoelectric patches and resonant shunt circuits. the present contribution discusses the modeling of piezoelectric patches coupled to shunt circuits, where the basics of resonant shunt circuits (series and parallel topologies) are presented. following, the devices used in passive control (piezoelectric patch and synthetic inductors) are analyzed from the electrical and experimental viewpoints. the modeling of multi-degree-of-freedom mechanical systems, including the effects of the passive damping devices is revisited, and, then a design methodology for the multi-modal case is defined. also, it is briefly reviewed the optimization method used for design purposes, namely the lifecycle model. finally, experimental results are reported, illustrating the succes
Multimodal vibration damping through piezoelectric patches and optimal resonant shunt circuits
Viana Felipe Antonio C.,Steffen Jr,Valder
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2006,
Abstract: Piezoelectric elements connected to shunt circuits and bonded to a mechanical structure form a dissipation device that can be designed to add damping to the mechanical system. Due to the piezoelectric effect, part of the vibration energy is transformed into electrical energy that can be conveniently dissipated. Therefore, by using appropriate electrical circuits, it is possible to dissipate strain energy and, as a consequence, vibration is suppressed through the added passive damping. From the electrical point of view, the piezoelectric element behaves like a capacitor in series with a controlled voltage source and the shunt circuit, commonly formed by an RL network, is tuned to dissipate the electrical energy, more efficiently in a given frequency band. It is important to know that large inductances are frequently required, leading to the necessity of using synthetic inductors (obtained from operational amplifiers). From the mechanical point of view, the vibration energy can be attenuated in a single mode, or in multiple modes, according to the design of the damping device and the frequency band of interest. This work is devoted to the study of passive damping systems for single modes or multiple modes, based on piezoelectric patches and resonant shunt circuits. The present contribution discusses the modeling of piezoelectric patches coupled to shunt circuits, where the basics of resonant shunt circuits (series and parallel topologies) are presented. Following, the devices used in passive control (piezoelectric patch and synthetic inductors) are analyzed from the electrical and experimental viewpoints. The modeling of multi-degree-of-freedom mechanical systems, including the effects of the passive damping devices is revisited, and, then a design methodology for the multi-modal case is defined. Also, it is briefly reviewed the optimization method used for design purposes, namely the LifeCycle Model. Finally, experimental results are reported, illustrating the success of using the methodology presented in passive damping applications applied to mechanical and mechatronic systems.
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